CHICAGO — Illinois Sen. Barack Obama, who will announce Saturday that he's running for the Democratic presidential nomination, says the brevity of his political résumé is his "greatest strength."

His work as a community organizer, civil rights attorney, constitutional law professor and state legislator "provides me with insights into solving problems at the federal level and at the local level and at the neighborhood level," Obama said in an interview with USA TODAY. That experience "is what's needed right now," he said.

Obama, 45, has been in the U.S. Senate for two years and served seven years in the Illinois Senate.

Only New York Sen. Hillary Rodham Clinton had more support for the nomination in a USA TODAY/Gallup Poll taken last month. Among respondents, 18% of Democrats and independents who lean Democrat supported Obama; 29% backed Clinton.

A year ago, Obama said, he didn't plan to run for president. But as he traveled across the USA campaigning for Democrats and signing his best-selling book The Audacity of Hope, he discovered "an enormous hunger for a new kind of politics — an enormous desire to end business as usual and to focus on a politics that brings us together."

That won't preclude "vigorous debates and serious differences" with rivals, Obama said. The Iraq war, which he opposed when other Democrats voted to authorize it, will be a "dominant issue," he said. "I'm proud that … I stood clearly and forthrightly in opposition." He supports a phased withdrawal of U.S. troops by March 31, 2008.

Obama also said:

•He and his wife, Michelle, worry about losing privacy. "We tend to be pretty private people, we don't like a lot of fuss," he said. "What I dread most is being away from my kids" — daughters Malia, 8, and Sasha, 5.

He'll make that sacrifice, he said, because he believes he can bring "people together to find common-sense, practical solutions" to economic, health care, education, energy and security problems.

•Although he would be the first African-American president, race is not "the main focus" of his campaign. If there are "symbolic benefits from it, that's great," he said.

•He hopes to generate "the kind of enthusiasm and interest" that motivates many people to make $5 or $10 donations online.

•He doesn't wake up every day certain he'll win. "I am absolutely convinced that …we've got a message that I think will appeal to the American people."